miguelszerman
Why do functions inside the keywords list passed as arguments to if aren’t called immediately? Is this unique to if?
# example.exs
defmodule Call do
def this(), do: IO.puts("this")
def that(), do: IO.puts("that")
end
defmodule Example do
def fun(keywords), do: :ok
end
IO.puts(
Example.fun(
[do: Call.this(), else: Call.that()]
)
)
IO.puts(
if(
true,
[do: Call.this(), else: Call.that()]
)
)
Output from file:
$ elixir example.exs
this
that
ok
this # expected 'this' and 'that' always to be called independently of the if the boolean evaluation
ok
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al2o3cr
ifis not a function, it is a macro. Macros run at compile-time and receive the AST representation of their arguments without any evaluation.The guide has a good example of implementing an
if-like macro:miguelszerman
Thanks!
Nicd
If it was written like this, would you still expect both to be called?
I suppose not, because what would be the point of
ifthen? But both of these codes are equivalent. In fact the latter is just syntax sugar for the former.miguelszerman
No, from the syntax sugar the logic flow is clear. My doubt came from reading Optional Syntax Sheet - Getting Started.
My question was about why the two codes work differently even though they are the same and not about how can I make sense of this.